Answer to Photo Quiz (See Pages 442–3)

Diagnosis: Echinococcal Cyst of the Fifth Thoracic Vertebra in an Otherwise Healthy Young Woman

Hydatid cysts affect the bones in a small percentage (0.5%–2%) of patients with echinococciasis. The spine is affected in ∼45% of patients with echinococcal bone disease [1]. Spinal infection is frequently asymptomatic and detected incidentally on imaging studies [2, 3]. Pain is the most common symptom. Radiographic findings of hydatidosis are rarely typical in bone, but CT or MRI may contribute to the diagnosis [4]. Echinococcal infection suspected on the basis of imaging studies can be confirmed by specific ELISA and/or Western blot serology.

The prognosis for spinal echinococcal infection has been considered very poor. The optimal treatment of symptomatic spinal echinococcal cysts is surgical resection [5, 6]. The medical therapy preferred for inoperable cysts (or for use in conjunction with surgical resection) is administration of albendazole, 400 mg twice a day by mouth for 4 weeks. The use of 2 more 4-week cycles of albendazole treatment (with 2-week rest periods without therapy) increases the efficacy of medical therapy [7].

Unfortunately, echinococcal cysts in bones, which are frequently not amenable to surgery, respond less well to drug treatment than do cysts in other locations. Recently, the combination of albendazole with praziquantel has been used for the medical treatment of patients with inoperable spinal hydatidosis, with promising results.

Echinococciasis continues to be an endemic infection in Greece, although a decreasing incidence has been noted during the past 2 decades. Our patient probably acquired echinococciasis by the ingestion of insufficiently washed fresh vegetables during her stay in her vacation home in rural Greece. There was no clinical or imaging evidence of echinococcal infection in sites other than her spine.

She underwent combined surgical and medical treatment. A left-sided thoracotomy was performed above the fifth rib, which was resected and kept as a bone graft. A big anterior para-vertebral cyst, originating from the fifth thoracic vertebra, was resected en bloc. The corrupted area of the vertebra was resected (mainly the posterior-left lateral part of the body of the fifth thoracic vertebra, as far as the posterior longitudinal ligament). The empty vertebral space was filled with a titanium cylinder that was packed with autologous graft from the resected rib. The stabilization was completed with screws inserted into the adjacent vertebrae and a rod connected to the screws.

Our patient also received adjunctive medical therapy with 3 4-week cycles of albendazole (400 mg twice a day by mouth, with 2-week rest periods without therapy between the cycles). One year after the operation she was well, and we found no clinical or imaging evidence of recurrence of her spinal echinococcal infection.

Figures and Tables

Figure 1

Anterioposterior chest radiograph showing a large mediastinal mass

Figure 2

CT scan of the chest (sagittal view), showing a paraspinal mass originating from the fifth thoracic vertebra

Figure 3

MRI scan of the thoracic spine (coronal view), showing clearly the cystic nature of the mass and the destruction of the fifth thoracic vertebra. Pathological examination of the excised cystic mass verified the diagnosis of echinococciasis.